Any Way to Offer Free Trial with Limited Fields & Then Add More Fields for Paid Subscription?

First I'll explain what we're trying to do, and then explain how far we've gotten so far.

What We're trying to do:
We're trying to offer a completely free 3-day trial (no credit card or payment information required) of a service that we sell a monthly subscription for. We're trying to make it so that to sign up for the free trial, only requires the following fields to be filled out:

• First Name
• Email
• Username
• Password

We want to have as few fields as possible on the free trial form, as the less fields there are, the more likely they are to sign up for the trial, which means we collect as many leads as possible. Once the free trial is over, they'll then need to sign up for a paid subscription (using Clickbank as the payment processor) to continue using the service.

Now, the regular monthly subscription sign-up form for a person who HASN'T signed up for a free trial requires the person signing up to fill out all the following fields:

• First Name
• Last Name
• Email
• Username
• Password
• Country
• City
• State
• Zip Code

We need to collect the address information of every paying customer, as it is important to our business to have that "lead" information.Clickbank does not collect address information on the purchase form, so we need to collect it on our end before sending them to the clickbank purchase page.

The problem we're running into is, if the user has signed up for the free trial, they can't sign up using the regular sign-up form, because amember won't allow you to sign up using the "sign up" form if you're already an existing member with a previously used username/email address. If you attempt to sign up using the regular sign up form that collects the additional information we need and you try to use the same username/email address that has already been used for the free trial account, it prompts you to sign into your account and purchase from within the "members.php" area in the "Add/Renew Subscription" area.

So if the user goes to the "Add/Renew" subscription area, and selects the monthly service we offer, and clicks the "order" button, they are immediately forwarded to the clickbank purchase page without having to fill out the additional fields of information we need to collect (their address information).

So, in essence, our question is how can we offer a free trial with very limited sign up fields, and then when the user wants to upgrade to a paid subscription, they are forced to provide us with their full first & last name as well as their billing address before being allowed to purchase the product?



What We've Got Completed So Far:
So far, we've got two completely different signup forms:

http://oursite.com/member/signup.php (this form is for paying customers)
http://oursite.com/member/signup2.php (this form is for totally free signups)

The first signup page (signup.php) requires their full name & billing address, as well as an email address, username & password. When they click the "signup" button, they are then forwarded to clickbank to make their purchase. After a successful purchase, they are then redirected back to our site to the appropriate clickbank thank you page.

The second signup page (signup2.php), only requires their first name, username, email address & password. When they click the signup button on that page, they are immediately redirected to a totally different thank you page saying "thanks for signing up for a free trial".

Those two pages work perfectly, and members are created as they should be in both cases, and the appropriate "Thank you" pages are seen by those signing up for their respective products.

The only way people ever see the signup2.php (the free trial signup form) is if they attempt to leave our site without signing up for anything. In other words, it's there basically as a last ditch "lead capture" event, which is the reason we're trying to keep the number of required fields so scarce.

All of that functions correctly, but the people who are signed up for the free trial, once it's run out, aren't able to then be forwarded to the regular sign-up form, because you can't sign-up using the same username or email address as one that is already in use. If they try to do that, it tells them to login and signup using the "add renew subscription" form, and if they signup from within that area of the members section, they aren't forced to give the information that we need about their full name & billing address.

I can also provide the real URLs to all signup forms mentioned above, but I don't want search engines finding my site here on this forum, particularly when potential subscribers will be googling our product name.

So if seeing my actual site & signup URLs would help somebody potentially provide a solution, please let me know and I'll provide them privately.